353
FXUS63 KABR 180755
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
255 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- A Marginal Risk (level 1 out of 5) for severe weather is posted
  for parts of south central SD and the I-90 corridor today and
  tonight. The main threats will be large hail and damaging winds
  along and south of a line from Pierre to Brookings.

- A Marginal Risk (level 1 out of 5) for severe weather has been
  issued for most of central and northeast SD on Wednesday and
  Wednesday night. Large hail and damaging winds will be the
  main threats.

&&

.DISCUSSION...
Issued at 254 AM CDT Tue Aug 18 2026

As of 2 AM CDT this morning, parts of our forecast area continue to
see a couple of storms tracking southeast across parts of south
central SD. These have been associated with mid level shortwave
energy and an upper jet streak working out of the Northern High
Plains into the Dakotas along with a weak sfc trough and an incoming
cold front sagging south across ND. Current temperatures generally
range between 60-70 degrees with light winds.

The main forecast challenge during the next few days will continue
to revolve around scattered storm chances as a northwesterly flow
aloft pattern remains persistent across the Northern Plains. Within
this flow, periodic shots of shortwave trough energy will rotate
across the region through mid week maintaining the active convective
pattern. What ends up being leftover from early morning storms
across parts of central and southeast SD along with shower activity
filling in across parts of northeast SD and west central MN will
exit the forecast area by mid morning. Dry conditions are then
expected to set up for the rest of the day as a cold front shifts
south across central and southern SD. This will help focus the
better instability across southern sections of the state into NE
during peak heating this afternoon. However, parts of south central
SD and the I-90 corridor will still see MLCAPE values of 1000-2000
J/kg develop. A 100+ kt jet streak setting up across SD should help
provide adequate deep layer shear of 40-50 kts. This will be within
a post-frontal environment and the early morning convection that
moved through that area will have sent in motion an outflow boundary
farther south into NE and KS by this afternoon and evening.
Nevertheless, given that more shortwave energy will work out of the
Northern High Plains across parts of western SD, a couple of strong
to severe storms cannot be ruled out this evening into early
Wednesday. SPC has maintained a Marginal Risk (level 1 of 5) for
severe weather across south central SD. Large hail to 1 inch in
diameter and damaging winds up to 60 mph will be the main threats.

Sfc high pressure will center itself across parts of ND during the
day today and into eastern SD/western MN tonight into Wednesday
morning. This will provide for a cooler overnight with temperatures
falling back into the 50s. As the high slips off to our south and
east during the day Wednesday, return flow will set up across
western and central SD by the afternoon. During this time, sfc low
pressure along with a pseudo warm front or sfc trough will work back
to the north and northeast Wednesday afternoon and Wednesday night.
Daytime heating will lead to MLCAPE values of 1500-2500 J/kg with
deep layer shear values of 35 kts. Another round of showers and
storms are expected to develop in the afternoon and evening as
another shortwave trough is progged to move through the region. A
few storms could turn severe with large hail up to 1 inch in
diameter and damaging winds up to 60 mph. SPC has posted a Marginal
Risk (level 1 of 5) for severe weather for central and northeast SD.

The outlook for the end of the week into the weekend will
essentially feature more of the same. An upper ridge across the
western CONUS will amplify as another sfc trough tracks southeast
across the eastern Dakotas and western MN on Thursday. Daytime
heating will lead to another unstable environment with increasing
instability, adequate deep layer shear and steep lapse rates. It
remains to be seen when and where any severe convection will set up
but our eastern zones will be in a more favorable window for some.
High pressure building southeast into the region Friday into
Saturday looks to give us a break from storms. Temperatures will
cool a bit back just below normal and humidity values will return to
more comfortable ranges.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1229 AM CDT Tue Aug 18 2026

Terminals KABR,KATY,KPIR,KMBG

A cluster of showers and thunderstorms continue to track
towards the southeast around 35kts over south central SD that
will continue to impact the KPIR terminal for the next hour or
so. Wind gusts could reach 30-35 kts. Otherwise we will continue
to isolated to scattered rain showers and thunderstorms across
central SD and portions of northeastern through the morning
hours. VFR cigs are forecast through the TAF period but may
briefly drop to sub VFR with any stronger rain shower or storm.
Winds will switch out of the northwest through the early morning
hours.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.

&&

$$

DISCUSSION...Vipond
AVIATION...MMM